Call from this # came in.  Didn't answer.  I called back.  Recording indicated looking for donations.  I pressed a key indicating I'm not interested.

Called at 7:49 pm on 4/12/16. Didn't answer, no message left. Blocked.

called me around 6pm. didn't leave a message

Scammer, buys lists to call. Could not identify how my number was acquired. Posing as someone trying to fund breast cancer treatments for women who can't afford it. Persistent and obviously on a per-successful-call payment system.

Search "sos wa American Cancer Research" results show up as American Institute for Cancer Research see https://www.sos.wa.gov/charities/search_detail.aspx?charity_id=192 showing their fundraisers used are Infocison Inc. https://www.sos.wa.gov/charities/search_detail_cfr.aspx?cfr_id=66 and Direct Response Consulting Services https://www.sos.wa.gov/charities/search_detail_cfr.aspx?cfr_id=96
You want the calls to stop? Notify the charity and fundraiser of your demand for placement on their "internal do not call list" under all databases. If they refuse or ignore your request start complaints to their BBB's and your state, their state, Attorney General's.  Florida has a policy that they're aware of https://www.fldnc.com/About.aspx